6,7,8,9-Tetrahydro-pyrido(1,2-a)pyrimidin-4-ones

ABSTRACT

6,7,8,9-Tetrahydro-2-aryl-9-alkyl-4H-pyrido(1,2-a)-pyrimidin-4ones, processes for their preparation, and methods for their use are disclosed herein.

[ Dec. 30,- 1975 [54] 6,7,8,9-TETRAI-IYDRO-PYRIDO(1,2-

A )PYRIMIDIN-4-ONES [75] Inventor: Harry Louis Yale, New Brunswick,

[73] Assignee: E. R. Squibb & Sons, Inc.,

Princeton, NJ.

22 Filed: Apr. 22, 1974 21 Appl. No.: 462,899

[52] US. Cl 260/251 A; 260/482 R; 260/483 424/251 [51] Int. Cl. C07D 471/04 [58] Field of Search 260/251 A [56] References Cited.

UNITED STATES PATENTS 3,585,198 6/1971 Meszaros et al'. 260/251 FOREIGN PATENTS OR APPLICATIONS 4,911 8/1972 Hungary OTHER PUBLICATIONS Adams et al., .I. Am. Chem. Soc., Vol. 74, 5491-5497 (1952).

Mendel, Chemical Abstracts, Vol. 77, (1972).

Yale et al., J. Heterocyclic Chemistry, Vol. 10, No. 2, pp. 123-125 (Feb., 1973).

Primary Examiner-Richard J. Gallagher Assistant Examiner-Diana G. Rivers Attorney, Agent, or Firml .awrence S. Levinson; Merle J. Smith; Donald J. Barrack [5 7] ABSTRACT 6,7,8,9-Tetrahydro-2-aryl-9-alkyl-4I-I-pyrido[1,2-a]- pyrimidin-4-ones, processes for their preparation, and methods for their use are disclosed herein.

5 Claims, No Drawings 6,7,8,9-TETRAHYDRO-PYRID(1,2-A)PYRIMI nm-a-omzs I BACKGROUND OF THE INVENTION Pyrido[ l ,2-a]pyrimidines (also known as homopyrimidazoles) are well knownin the heterocyclic chemistry art. U.S. Pat. No. 3,585,198, issued June 15, I971, describes much of the literature relating to this type of compound. Additionally, the patent contains a broad sweeping disclosure of GI-pyrido[l,2- a]pyrimidines having numerous possible substituents at every possible position on the heterocyclic ring system. This disclosure encompasses not only 4H-pyrido[l,2- a]pyrimidines per se, but also the 6,7, 8,9-tetrahydro and l,2,3,4,6,7,8,9-octahydro derivatives. 1

It has now been suprisingly found that certain pyrido- [l,2-a]pyrimidines, i.e., 6,7,8,9-tetrahydro derivatives of pyrido[ l ,2-a]pyrimidines having a phenyl (or substituted phenyl) group in the 2-position,a keto group in the 4-position and an alkyl group in the 9-position, possess useful central nervous-system depressant activity. The analagous pyrido[l,2-a1pyrimidines that are unsaturated in the 6,7-and 8;9-positions, and those in which both rings are saturated, are devoid of this type of activity. I

SUMMARY OF THE INVENTION Compounds having the structure I have useful pharmacological activity. In formula I, and throughout the specification, the symbols have the following meanings.

R can be phenyl or phenyl having one or two substituents selected from alkyl, alkoxy, halogen, and trifluoromethyl;

R can be hydrogen or alkyl; and

R can be alkyl.

The term alkyl" as used throughout the specifica tion refers to a straight or branched chain saturated hydrocarbon group having 1 mo carbon atoms. Exemplary alkyl groups are methyl, ethyl, propyl, isopropyl, butyl, t-butyl, isobutyl, hexyl, etc. Alkyl groups having I to 3 carbon atoms are preferred.

The term alkoxy as used throughout the specification refers to groups having the formula Y-O-, wherein Y is alkyl as defined above. Alkoxy groups having 1 to 3 carbon atoms are preferred.

The term halogen as used throughout the specification refers to fluorine, chlorine, bromine and iodine; chlorine and bromine are the preferred halogens.

DETAILED DESCRIPTION OF THE INVENTION 0 Il R,i'iiHC-OR,

III I N NH yields the corresponding 2-aryl-9-aIkyl-4H pyrido[1,2- a]pyrimidin-4-one having the structure:

The reaction is novel, and 'as' such, it constitutes "a part of this invention. The novel reaction is run in a hydroxyalkyl ether solvent, e.g., ethylene glycol monomethyl ether or ethylene glycol monoethyl ether under reflux conditions for 1 day to 10 days, preferably 2 days to 5 days. It is a critical feature of this reaction that p-toluenesulfonic acid be added to the reaction mixture in an amount of from about 0.2 mole to 0.5 mole per mole of aminopyridine; the use of about 0.25 moleof p-tolu enesulfonic acid per mole of aminopyridine is preferred. I v

Alternatively, the intermediates of formula IV wherein R ishydrogen can be prepared by reacting an aminopyridine of formula III with an aminocinnamatehavingthe structure:

The reaction can be run in an aromatic solvent, e.g., xylene or dicthylbenzene, at elevated temperatures, preferably C to 190C. Depending of course on the particular reactants and the temperature of the reaction, the reaction will take from 1 day to 4 days. This procedure is not applicable when R is phenyl substituted with iodine.

Catalytic reduction of the pyrido[l,2-a1pyrimidin- 4-oncs of formula IV to the corresponding 6,7,8,9-tetrahydro derivatives is accomplished using procedures well known in the art. The preferred catalyst is Raney nickel; the use of a platinum or palladium oxide catalyst yields the octahydro derivatives of the compounds of formula IV rather than the desired tetrahydro derivatives.

The 2-amino-3-alkylpyridine starting materials of formula III are well known in the art; see for example, L. E. Tennenbaum, Alkylpyridines," Vol. 14, Pt. 2, of The Chemistry of l-Ieterocyclic Compounds, Interscience, 1961, pp. -298; R. G. Micetich, Vol. 14,

with an ester having the structure:

In the presence of a sodium alkoxide (e.g., sodium methoxide); see for example, Organic Reactions, Vol. 1, Chapter by C. R. Hauser and B. E. Hudson, Jr., p. 266.

The 3-aminocinnamates of formula V are known, and can be readily prepared by reacting a Grignard reagent of the structure:

Vlll R,-Mg-X wherein X is chlorine or bromine, with a'l-cyanoacetate having the structure:

' The novel '6,7,8,9-tet'rahydro-2-aryl-9-alkyl-4H pyrido[ l ,2-a]pyrimidin-4-ones of this invention can be converted, using procedures well known in the art, into their'pharmaceutically acceptable acid-addition salts. lllustrative'of thesalts contemplated for use in this invention are the hydrohalides (e.g., the hydrochloride and hydrobromide), sulfate, nitrate, tartrate, phosphate, maleate, fumarate, citrate, succinate, methanesulfonate, benzenesulfonate, toluenesulfonate, and the like.

The compounds of formula I, and the pharmaceutically acceptable acid-addition salts thereof, are useful in mammalian species such as rats, dogs, monkeys and others, as central nervous system depressants and can be used as tranquilizers for the relief of anxiety and tension states in the same manner as chlordiazepoxide.

For this purpose these compounds can be incorporated in a conventional dosage'form such as tablet, capsule, injectable 'or the like, along with the necessary carrier material, excipient, lubricant, buffer or the like, for oral or. parenteral administration in single or divided doses of about 1 to lOO mg./kg./day, preferably about 5 to 15 mg./kg., two to four times daily.

EXAMPLE 1 A. 6,7,8,Q-Tetrahydro-9-methyl-2-phenyl-4l-lpyrido[ l ,2-alpyrimidin-4-one 9-Methyl-2-phenyl-4H- pyrido[ l ,2-a]pyrimidin-4-one METHOD 1 i A mixture of 9.6 of ethyl 3-aminocinnamate, 5.4 g of 2-amino-3-methylpyridine, and 50 ml of diethylbenzene is heated in an oil bath at l-l C for about 21 hours. No solidseparates on cooling the reaction mixture. The volatiles are removed in vacuo. and the residue is cooled to give 1.79 g of solid, melting point l64l7lC. Recrystallization from ethyl acetate gives 1.2 g of the title compound, melting point ll 82C.

METHOD 2 A solution of 10.8 g of 2-amino-3-methylpyridine, 38.4 g of ethyl benzoylacetate, 5.0 g of p-toluenesulfonic acid, and ml of ethyleneglycol monomethyl ether is heated under reflux for nine days, and then cooled. The crystalline solid that separates is filtered and air-dried to give 5.7 g of material, melting point l78182C. Recrystallization from ethyl acetate gives 3.82 g of the title compound, melting point l82-l83C.

B. 6,7,8,9-Tetrahydro-9-methyl-2-phenyl-4H- pyrido[ l ,2-a]pyrimidin-4-one A suspension of 3.4 g of 9-methyl-2-phenyl-4H- pyrido[ l ,2-a]pyrimidin-4-one, 4 g of Raney nickel, and 200 ml of absolute ethanol is hydrogenated [50 psi/25C] to give 3.4 g of product, melting point 6875C. Recrystallization from pentane yields 2.5 g of the title compound, melting point 78S0C.

EXAMPLES 2 8 Following the procedure of Example 1, parts A & B (utilizing Method 1 in part A), but substituting the compound listed in column 1 below for ethyl 3- aminocinnamate, and the compound listed in column ll below for 2-amino-3-methylpyridin e, the compound listed in column [II is obtained.

Column ll Column Ill CH3(CH2)2 z z a c1 N NH N (CH3)2CH f rcmcu h FD-Q-Br N z s M cu NH2 EXAMPLES 9 26 Following the procedure of Example 1; parts A & B,

Continued compound listed in column I below for ethyl benzoylacetate and the compound listed in column ll below for 2-amino-3-methylpyridine, the compound listed in (utilizing Method 2 'in part A), but substituting the 35 column III is obtained;

. iv o ll u 12 QC-CHfO-C Column ll Colum'n Ill Continued M Column l Column II M CH3 II n (CH3)2CH CCHCOCH 23 l 3 cutcn l N CH CH3 1 I r a 3 (CH3)3C CH3 N NH2 N II II CH3 24 ccH c-ocH CH3 IN 3 F c l 3 N NH2 N I cr- FC 2M... H 3

3 N 25 \Q, 2 2 5 WY(CHZ)4CH3 64 l N N B H I Br N 2 0 3 O 0 CH3 i g CH c o H (iH2)3 2b 2 s l\ CH 0 CH3 (CH2)3O N NH N CH CH3 2 o 3 EXAMPLE 27 in Example l l lin 50 ml of anhydrous ether, at 0C, is

6,7,8,9-Tetrahydro-9-methyl-2-phenyl-4H-pyrido- [l,2-a]pyrimidin-4-one, salt with p-toluenesulfonic acid, dihydrate To a stirred solution of 2.40 g of 6,7,8,9-tetrahydro- 9-methyl-2-phenyl-4H-pyrido[ l ,2-a]pyrimidin-4-one (prepared as described in Example 1 in ml of warm water is added a solution of 1.90 g of p-toluenesulfonic acid monohydrate in 25 ml of warm water. The solution that forms is clarified by filtration, cooled, frozen, and lyophilized to give 4.20 g of the title compound as a free-flowing solid.

EXAMPLE 28 9-Ethyl-6,7,8,9-tetrahydro-2-(a,a,a-trifluoro-mtolyl)-4H-pyrido[l,2-a]pyrimidin-4-one, salt with maleic acid To a stirred solution of 3.22 g of 9-ethyl-6,7,8,9-tetrahydro-2-(a,a,a-trifluoro-m-tolyl )-4H-pyrido[ l ,2-a]- pyrimidin-4-one (prepared as described in Example 4) in 25 ml of acetonitrile is added a warm solution of 1.16 g of maleic acid in 15 ml of acetonitrile. The mixture is stirred as it cools to room temperature. The solution is then filtered and cooled to give the title compound.

EXAMPLE 29 2-[m-(n-l-lexyloxy)phenyl]-3-methyl-9-(2-propyl)- 6,7,8,9-tetrahydro-4H-pyrido[ l ,2-a]pyrimidin-4-one, hydrochloride To a solution of 3.62 g of 2-[m-(n-hexyloxy)phenyl]- 3-methyl-9-(2-propyl)-6,7 ,8 ,9-tetrahydro-4H- pyrido[l,2-a]-pyrimidin-4-one (prepared as described added, dropwise, 10 ml of N ethereal hydrogen chloride; a precipitate forms during the addition. Subsequently, the mixture is stirred for 15 minutes at 0C, and filtered rapidly to give the title compound.

What is claimed. is:

l. A compound having the structure 

1. A COMPOUND HAVING THE STRUCTURE
 2. A compound in accordance with claim 1 wherein R1 is phenyl.
 3. A compound in accordance with claim 1 wherein R2 is hydrogen.
 4. A compound in accordance with claim 1 wherein R2 is alkyl.
 5. The compound in accordance with claim 1 having the name 6,7, 8,9-tetrahydro-9-methyl-2-phenyl-4H-pyrido(1,2-a)pyrimidin-4-one. 